Most fresh water in the UK is at risk
from human activities.
Modern crop protection products are stringently regulated so that their risk of causing damage to the water environment is remote. To protect drinking water the allowable limit for any pesticide is 0.1 parts per billion. this is not based on science as the permitable health limits would be much greater.
Water Companies do treat for many contaminants, many more toxic than pesticides, but few must be removed to the 0.1ppb level. This 0.1pbb level is the equivalent of 1gm of pesticide in a stream that is 33 kilometres long, a metre wide and a third of a metre deep. Not much!! It is not surprising, that at such minuscule levels, pesticides are occasionally detected in natural waters.
Research (Bayer CropScience - Cherwell Study 2000) has shown that the very small drips and splashes that take place during sprayer filling, along with external sprayer washing can lead to a substantial portion of the pesticide contamination found in water.
This is preventable!